COS 283-4 - Multi-year drought impacts across 70 terrestrial ecosystems: results from the International Drought Experiment (IDE)

Thursday, August 10, 2023

2:15 PM – 2:30 PM PDT

Location: D140

Presenting Author(s)

TO

Timothy Ohlert

Colorado State University, United States

Coauthor(s)

MS

Melinda D. Smith

Professor
Colorado State University
Fort Collins, Colorado, United States
MA

Maggie Anderson

University of Minnesota, United States
MA

Meghan L. Avolio

Assistant Professor
Johns Hopkins University
Baltimore, Maryland, United States
AC

Anping Chen

Colorado State University, United States
SC

Scott L. Collins

Distinguished Professor
University of New Mexico
Albuquerque, NM, United States
JD

Jeffrey Dukes

Senior staff scientist
Carnegie Institution for Science, Division of Biosphere Sciences & Engineering
Stanford, California, United States
AF

Andrew Felton

Montana State University, United States
MH

Meghan T. Hayden

PhD Student
University of Colorado - Boulder
Boulder, Colorado, United States
MH

Martin Holdrege

Postdoctoral Researcher
USGS Southwest Biological Science Center, United States
AJ

Anke Jentsch

Professor of Disturbance Ecology and Vegetation Dynamics
University of Bayreuth
Bayreuth, Bayern, Germany
AK

Alan Knapp

Colorado State University, United States
SP

Smriti Pehim Limbu

Johns Hopkins University
Baltimore, MD, United States
SM

Seth M. Munson, Ph.D

Research Ecologist
US Geological Survey
Flagstaff, Arizona, United States
OS

Osvaldo Sala

Professor
Arizona State University, United States
Ingrid J. Slette

Postdoctoral Scholar
National Center for Ecological Analysis and Synthesis, United States
KW

Kate Wilkins

Denver Zoo, United States
LY

Laura Yahdjian

Universidad de Buenos Aires, Argentina
IN

IDE Network

Colorado State University, United States

Abstract: Climate models predict that droughts will increase in duration and extremity this century across terrestrial ecosystems. However, compared to our knowledge of short-term drought effects, we know much less about how drought impacts will unfold over time to affect aboveground net primary production (ANPP) in terrestrial ecosystems. And while some evidence suggests that the negative effects of drought on ANPP become less pronounced over time as drought-tolerant species potentially increase in abundance, other evidence suggests that the negative effects of drought magnify as drought duration increases. To address this discrepancy, we organized a coordinated distributed network of multi-year drought experiments known as the International Drought Experiment (IDE). At each experiment site, rainout shelters were deployed for three years to simulate a 1-in-100 year extreme drought based on the long-term climate record of each IDE site. ANPP data were collected annually and drought responses were quantified as the log response ratio of ANPP in treatment plots compared to the long-term average ANPP for each site. Based on data from 70 IDE sites across six continents, we asked: do drought effects on ANPP in grassland and shrubland ecosystems increase or decrease over three consecutive drought years?

The mean drought severity across all sites and years was -47% of mean annual precipitation. We found that the response of ANPP to drought severity generally increased over time (p = 0.03). And, when drought in the previous year was most severe, ANPP losses were greatest (p < 0.01). That is, we observed the greatest ANPP losses when precipitation was extremely low in both the previous and the current year of drought. Overall, our findings suggest that the negative effects of drought on ANPP can accumulate over time, particularly when drought events are sufficiently extreme. Given the potential for substantial reductions in ecosystem function as drought severity and duration increase, there is a pressing scientific and societal imperative to better understand the impacts of multi-year drought across terrestrial ecosystems globally.